Better comments in SkXfermodeInterpretation

src/core/SkXfermodeInterpretation.h

Index: src/core/SkXfermodeInterpretation.h
diff --git a/src/core/SkXfermodeInterpretation.h b/src/core/SkXfermodeInterpretation.h
index f559b33a7dfe18ccdc63bd36396b68ff53f995c1..d0a420f383d4ece6a1e77286af0e87c9d5449e8e 100644
--- a/src/core/SkXfermodeInterpretation.h
+++ b/src/core/SkXfermodeInterpretation.h
@@ -10,13 +10,21 @@
 
 class SkPaint;
 
-/** By analyzing the paint, we may decide we can take special
-    action. This enum lists our possible actions. */
+/**
+ *  By analyzing the paint, we may decide we can take special
+ *  action. This enum lists our possible actions.
+ */
 enum SkXfermodeInterpretation {
-    kNormal_SkXfermodeInterpretation,      // draw normally
-    kSrcOver_SkXfermodeInterpretation,     // draw as if in srcover mode
-    kSkipDrawing_SkXfermodeInterpretation  // draw nothing
+    kNormal_SkXfermodeInterpretation,      //< draw normally
+    kSrcOver_SkXfermodeInterpretation,     //< draw as if in srcover mode
+    kSkipDrawing_SkXfermodeInterpretation  //< draw nothing
 };
+
+/**
+ *  Given a paint, determine whether the paint's transfer mode can be
+ *  replaced with kSrcOver_Mode or not drawn at all.  This is used by
+ *  SkBlitter and SkPDFDevice.
+ */
 SkXfermodeInterpretation SkInterpretXfermode(const SkPaint&, bool dstIsOpaque);
 
 #endif  // SkXfermodeInterpretation_DEFINED